TRANSITION METAL CLUSTERS

CONTAINING FERROCENYL DIPHOSPHINE

A Dissertation

FOR THE DEGREE OF

MASTER OF SCIENCE IN CHEMISTRY

By Suvendu Kumar Barik

Roll No- 412CY2004

Under the Guidance of

Dr. Saurav Chatterjee

Department of chemistry

National Institute of Technology, Rourkela

Odisha -769008

CERTIFICATE

This is to certify that the dissertation entitled “TRANSITION METAL CLUSTERS

CONTAINING FERROCENYL DIPHOSPHINE” being submitted by Suvendu Kumar

Barik to the Department of Chemistry, National Institute of Technology, Rourkela, Orissa, for

the award of the degree of Master of Science is a record of Bonafide research carried out by him

under my supervision and guidance. To the best of my knowledge, the matter embodied in the

dissertation has not been submitted to any other University / Institute for the award of any

Degree or Diploma.

N.I.T. Rourkela Dr. Saurav Chatterjee

Date (Supervisor)

ACKNOWLEDGEMENT

I owe this unique opportunity to place on record my deep sense of gratitude &

indebtedness to Dr Saurav Chatterjee, Department of Chemistry, National Institute of

Technology, Rourkela for his scholastic guidance, for introducing the present project topic and

for his inspiring guidance and valuable suggestion throughout the project work. I most gratefully

acknowledge his constant encouragement and help in different ways to complete this project

successfully.

I would also like to acknowledge Prof. N. Panda, Head of the Chemistry Department,

National Institute Of Technology, Rourkela for providing me the necessary facilities for making

this research work a success.

My sincere gratitude is to Vijayalakshmi Tirkey for her overall guidance, immense help,

valuable suggestions, constructive criticism & painstaking efforts to carry out the experimental

work.

I also like to thank my lab seniors Sasmita Mishra, Avishek Ghosh and all my friends for

their co-operation and continuous encouragement throughout the entire period of the project and

special thanks for making a friendly atmosphere in the laboratory.

In the end I must record my special appreciation to my parents and GOD who have

always been a source of my strength, inspiration & my achievements.

Rourkela

Date: Suvendu Kumar Barik

DECLARATION

I hereby declare that the research work incorporated in this dissertation entitled “TRANSITION

METAL CLUSTERS CONTAINING FERROCENYL DIPHOSPHINE ” is an original research work carried out by me in Chemistry department, Nation Institute of

Technology Rourkela under the supervision of Dr. Saurav Chatterjee.

Date:

Suvendu Kumar Barik

Place:

CONTENTS

CHAPTER- 1:INTRODUCTION 1.1 Transition metal clusters

1.2 Main group elements in transition metal clusters

Chalcogenide metal clusters

1.3 Transition metal cluster containing phosphine

1.4 Cluster containing ferrocenyl diphosphine

(a) Heteronuclear

(b) Heteronuclear

1.5 Ferrocenyl diphosphine substituted metal chalcogen clusters

1.6 References

CHAPTER- 2:TRANSITION METAL CLUSTERS CONTAINING

FERROCENYL DIPHOSPHINE

2.1 Introduction

2.2 Experimental Section

2.2.1 General procedures

2.2.2 Reaction of [Fe3Te2(CO)9] with dppf (diphenylphosphino ferrocene)

2.2.3 Low temperature reaction of [Fe3Te2(CO)9] with dppf

2.2.4 Reaction of [Fe3Se2(CO)9] with Bis-(diphenylphosphino)ferrocene

2.2.5 Synthesis of W(CO)5THF and [Fe3Se2(CO)8(2-dppf)W(CO)5], (Se2BlackW(CO)5

2.3 Results and Discussion

2.4 Conclusion

2.5 References

CHAPTER 1

INTRODUCTION

1.1. Transition Metal Clusters

A transition metal cluster contains two or more transition metal atoms bonded by direct

or substantial metal-metal bonding and forms a three dimensional polyhedral geometry. The

transition metals bridged by main group elements form especially robust cluster and they

constitute link between homogeneous and heterogeneous catalysis. Transition metal clusters

show high activity in heterogeneous catalysis and selectivity in the homogeneous catalysis [1].

Literature survey shows the presence of some cluster complexes in various enzymes such as

hydrogenase and their activity in biocatalysis [2] (Figure 1.1). Clusters have also been used as

potential candidate in the area of material science and in advanced opto-electronic materials for

their non-linear optical property [3].

Fe Fe

CO

S

Fe4S4

S

CO

CN

S

HN

Cys

Figure 1.1: Proposed active site structure of the[Fe-Fe] hydrogenase enzyme

Some metal cluster contains π-donor ligands like cyclopentadienyl, alkene, akyne, known

as π-donor cluster having high oxidation state metal atom. The transition metal cluster which

contains π-acceptor ligands like CO, PPh3 are known as π-acceptor clusters with low oxidation

state metal fragments. The transition metal clusters containing the CO ligand are found to bind

with metals in a variety of bonding modes and other ligands like phosphine, halides, isocyanides,

alkenes and hydrides also stabilizes the clusters. The clusters act as "electron reservoirs" and can

access to multiple redox states as the number of metals increases. It has been seen that clusters

can undergo rearrangement through the breaking of the metal-metal bond thereby allowing for

the organic substrate to react with an accessible coordination site on the metal leading to organic

transformations [4]. It has been studied that clusters can effectively catalyze reactions in

biphasic medium so that the fragments remains in the aqueous phase and the organic substrates

remain in the organic phase [5].

1.2. Main group elements in Transition metal clusters

Clusters are described as models for intermediate in catalysis and are also used as

catalysts. From the recent research development it has been found that many transition metal

clusters are unstable and degrade when studied for organic transformation and catalysis. The

main group elements can be used as bridging elements forming the framework of the clusters

which are necessary for catalysis. The main group elements can be used as promoters to give

higher yields and better selectivity in many commercial catalytic reactions and also act as sites

for reactivity. Various research groups have proved in the field of cluster chemistry that these

materials consists of nonlinear optical properties for their probable application in optoelectronics

[6]. The formation of metal-metal bond is related to the size of the central main group element

which helps in their stability. The smaller main group elements helps in metal-metal bonding

while heavier main group elements generally bridge more open structures. The substituent on

main group elements and the mode of binding are responsible for the number of electrons

contributed to the clusters by main group fragments necessary for stabilizing the clusters. The

bridging ligand is preferred to promote the formation and stabilization of transition metal cluster

complexes [7-10]. The main-group elements incorporated into transition-metal carbonyl clusters

enhance the structural and reactivity features. The main-group-element ligand can be used to

bridge between different metal fragments in cluster growth reactions.

M

E

MM E

M

M

M

E

M

M

M

E

M

M

M

M M

M

E

M

M

M

E

E

M

1 2 3

45 6

7

E=Group,13-16 elements,M=Transition metals

M E M

Figure 1.2: Structural geometries of transition metal cluster with main group elements.

Adams et. al. had reported recently the main group element containing rhenium cluster

[Re(CO)4-(μ-BiPh2)]3 by heating [Re2(CO)8Bi2Ph4] (Figure 1.3) [11].

Re

Bi

Re

Re

Bi

Bi

Ph

PhPh

Ph

Ph Ph

OC

OCCO

CO

CO

CO

COOC

CO

OC

OCCO

Figure 1.3. [Re(CO)4(μ-BiPh2)]3

1.3. Chalcogenide metal clusters

Incorporation of the chalcogen as bridging ligand into the clusters unit results in the

formation of unique structural features and unusual reactivities [12]. Chalcogen elements and

transition-metal combine together to form cluster units showing interesting geometries and

forming new coordination and thereby acting as precursors for synthesis of new materials [13-

15]. Chalcogen ligand show a wide variety of bonding modes when these are incorporated into

transition metal carbonyl cluster frameworks. Chalcogen are used in metal cluster as these

ligand bridges with metals thereby preventing the degradation of the fragments as the clusters are

usually susceptible during catalytic processes [16]. The clusters containing the bond between

transition metal and group-16 elements such as S, Se, and Te are subjected to recent studies as

these main group elements act as bridges between different metal atoms in clusters and also

helps in stabilizing ligand which prevent their fragmentation. Chatterjee et al very recently

discussed room temperature reactions of dppe with metal clusters [Fe3( 3-Te)2(CO)9], [Fe3( 3-

Te)2(CO)8PPh3] to obtain different types of chalcogenide metal-phosphine clusters, one of them

showing the bridging mode where two cluster unit are attached by the dppe unit[(CO)18Fe6( 3-

Te)4 -PPh2(CH2)2PPh2}] (Figure 1.4) [17].

]

Fe

TeTe

Fe

Fe

CO

OC

COOC

CO

CO

CO

CO

Ph2P

H2C

CH2

Ph2P

OCFe

TeTe

Fe

FeCOOC

CO

COOC

OCCO

OC

OC

Figure 1.4. [(CO)18Fe6( 3-Te)4 -PPh2(CH2)2PPh2}]

1.4. Phosphine incorporated transition metal cluster

Phosphines, PR3, are the ligands in which the electronic and steric properties can be

adjusted in a desired way over a wide range by varying the organic group (R) [18]. Various

research groups were involved in the synthesis of transition metal clusters containing phosphine

ligands by ligand substitution reaction of the carbonyl containing metal clusters [19-23]. Several

metal catalysts contain mono and bidentate phosphine ligands which are very important in Heck,

Suzuki and Buchwald-Hartwig cross coupling reactions as the choice of proper phosphines at the

metal centers of the catalysts influences the reactivity of the participating species in the catalytic

cycle [24-27]. The phosphines are classified into monodentate phosphine with only one

phosphorus atom binding to the metal center of the cluster unit, bidentate phosphines when two

phosphorus atoms are linked to metal atoms of the cluster unit and polydentate phosphines with

more than two phosphorus atoms binding to the metal centres of the cluster unit. The common

monodentate ligands like triarylphosphines, tricyclohexylphosphine, tri(tertbutyl)phosphine and

trimethyl phosphine are of much interest as the chiral monodentate phosphines are found to be

very effective in asymmetric homogenous catalysis [28](Figure 1.5). The tertiary phosphine

ligands co-ordinate with the late metal centers of the metal complexes as they stabilize the low-

valent metal intermediates thus allowing high activity of the catalysts. They react with the metal

clusters and possess simple terminal, edge-bridged and face- capped positions for facile P-C

bond formation and cleavage, so that metal skeletal transformations can be understood. Hence,

the bonding modes adopted by phosphine ligand upon co-ordination are explored largely.

P

An

Me

Hex -c

(S)-CAMP

PPh3

neomethydiphenylphosphine [NMDPP]

Figure 1.5. Monodentate phosphine

Literature survey shows that phosphine ligands play a major role for the synthesis of

polynuclear units of the clusters. Low temperature reaction of PBu3 with triosmium clusters led

to the formation of mononuclear complexes Os(CO)4(PBu3) and Os(CO)3(PBu3)2. Adam’s et al.

reported a heterometallic platinum-osmium cluster complex, [Pt2Os3(CO)10(PtBu3)2] in which

two monodentate phosphines are bonded to the platinum metal centres (Figure 1.6) [29].

Os Os

Os

Pt

PBut3

Pt

PBut3

CO

CO

O

OO

O

OC

OC

OC

CO

Figure 1.6. [Pt2Os3(CO)10(PtBu3)2]

Shawkataly et al. recently reported six trinuclear substituted complexes of the type

[Ru3(CO)9(arphos)(L)] synthesized from the substitution reaction involving [Ru3(CO)10(arphos)]

with various monodentate phosphine ligands like PCy3, PPh3, P(C6H4F-m)3, P(C6H4F-p)3,

P(C6H4Cl-p)3 and PPh(C6H4OMe-p)2 using the thermal synthetic method (Figure 1.7) [30].

Ru

Ru

Ru

OCCO

CO

CO

OC

CO

OC CO

CO

P

CH2

CH2

As

Ph

Ph

PhPh

L

Figure 1.7. [Ru3(CO)9(arphos)(L)]

{L = PCy3, PPh3, P(C6H4F-m)3, P(C6H4F-p)3, P(C6H4Cl-p)3, PPh(C6H4OMe-p)2}

Bidentate ligands like diphosphines give support to the multimetallic framework and also

help to bind two or more cluster fragments resulting in cluster stability and structural diversity of

higher nuclear cluster. Some diphosphine ligands used in cluster substitution reaction have been

shown in Figure 1.8.

H

H

PPh2

PPh2

O

O

(S,S)-DIOP

PPh2

PPh2

(S)-2,2'-bis(diphenyl phosphino)-1,1'-binapthyl[(S)-BINAP]Ph2P PPh2

bis(diphenylphosphino)methane[dppm]

Ph2P PPh2

1,2-bis(diphenylphosphino)ethane[dppe]

PMe2Me2P

PMe2Me2Pbis(dimethylphosphino)methane[dmpm]

1,2-bis(dimethylphosphino)ethane[dmpe]

Figure 1.8. Different types of bidentate phopshine ligands

Research group of Zavras reported the structure of [Ag3{(Ph2P)2CH2}3( 3-Cl)( -H)]BF4

in which [Ag( -Cl)( 3-H)] core is found to be tetrahedral and the two phosphorus atoms of the

dppm ligands binds the Ag metals in intra-bridging mode (Figure 1.9) [31].

Ag

Ag

Ag

Cl

P

PH2C P

P

CH2

P P

C

H2

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Ph PhPh

Figure 1.9. [Ag3-{(Ph2P)2CH2}3( 3-Cl)( -H)]BF4

Zhang et al. studied the tricobalt cluster, [PhCCo3(CO)9] which undergoes facile ligand

substitution with 1,8-bis(diphenylphosphino)naphthalene (dppn) forming the cluster containing a

chelating dppn ligand, [PhCCo3(CO)4(µ-CO)3(dppn)] involving three bridging CO groups in the

solid state structure (Figure 1.10) [32].

Os Os

OsPh2

P

PPh2

(CO)4

(CO)4 (CO)2

Figure 1.10: [1,1-Os3-(CO)10(dppbz)]

1.5. Cluster containing ferrocenyl diphosphine

(a) Homonuclear

Homonuclear clusters contain same type of metal in its cluster cage. These homonuclear

cluster containing ferrocene have very important due to its potential application in biosensors,

catalysis etc. The complex [Pd3( -dppf)(dppf)( 3-S)2Cl2]·2 CH2Cl2 reported by Yeo and group

shows dppf coordinating the cluster unit in both the chelating and bridging mode (Figure 1.11)

[33].

Fe

Pd

PdPd

S S

Cl

Cl

P

P

Ph Ph

Ph

Ph

Fe

P

P

PhPh

Ph

Ph

Figure 1.11. [Pd3( -dppf)(dppf)( 3-S)2Cl2]·2 CH2Cl2

The complex [Co2(1-dppf)(

2-(MeO2C)2C2)(CO)5] is the sole structure containing an

1-

coordinating dppf reported by McAdam group [34]. Zhuravel group discussed the diphosphine

ligand which has an anticlinal eclipsed arrangement, with an angle of 154.9° in [Pt2(dppf)2-( -

H)( -pms)]Br, which is a dinuclear -alkylidene -hydride cation, where each dppf behaves as

2-chelating and assumes a synclinal staggered conformation (Figure 1.12) [35].

P

P

Ph Ph

Ph Ph

Pt Pt

P

P

Ph

PhPh

Ph

CH

CH2Ar

H

Fe Fe

+

Ar = p-MeOC6H4

Figure 1.12. [Pt2(dppf)2-( -H)( -pms)]+

The complex, [Au2(dppf)( -pdt)], is an 1,

1-intrabridging cluster complex, although the Au–Au

separation in this molecule (3.060(1) A,) is considered a bond, it is very much long as compared

to other clusters (Figure 1.13) [36].

Fe

P

P

Ph Ph

Ph Ph

Au

Au

S

CH2

S CH2

CH2

Figure 1.13. [Au2(dppf)( -pdt)]

(b) Hetero nuclear

Heterometallic clusters are compounds having two or more different metals forming the

cluster core. Group 14 element containing transition metal clusters have been studied by

Mackay v, Lewis and Braunstein [37-39]. The heterometallic clusters are interesting due to their

synthetic studies and structural bonding pattern and their application in the field of catalysis.

Nyholm et al. described the first heterometal gold cluster, [Au2Fe(CO)4(PPh3)2], Collins et al.

synthesised [Au2Ru3( 3-S)( -dppf)(CO)9] having the metal framework containing trigonal

bipyramidal or distorted trigonal bipyramidal Au2Ru3 groups (Figure 17) [40].

Ru

Ru

Ru

Au

Au

OCCO

CO

OC

OC

CO

COOC

S

FeP

P

Ph

Ph

Ph

Ph

Figure 1.14. [Au2Ru3( 3-S) ( -dppf)(CO)9]

In one of the very recent cluster [Hg{Fe[Si(OMe)3](CO)3(dppm)}2Pd], an unusual Fe-

Hg-Pd bond, with a palladium (0) fragment has been observed. The cluster was prepared from

the reaction of complex [Hg{Fe[Si(OMe)3](CO)3(dppm)}2] with [Pd2(dba)3]. The compound has

been stabilized by an unusual heterometallic Pd-Hg bonding with d10–d10 interaction (Figure

1.15) [41].

Pd

PPh2

(OC)2Fe Hg Fe(CO)3

PPh2

Ph2P

PPh2

Si(MeO)3

Figure 1.15. [Hg{Fe[Si(OMe)3](CO)3( -dppm)}2Pd],

1.6. Ferrocenyl diphosphine substituted metal chalcogen clusters

Ferrocene containing chalcogen metal clusters has shown a rapid interest. Various

methodologies and substitution effects has been observed on this cluster moiety in order to study

the substitution effects on triangular clusters M3(μ-S2)(CO)9 based on the stabilizing effect

exerted by capping sulfide ligands. The isosceles triangle provides a model for the study of co-

ordination mode and side selectivities. The incoming diphosphine is represented by 1,1’-bis

(diphenylphosphino)ferrocene (dppf) which has been shown to exhibit a variety of co-ordination

modes under very similar conditions. Diphosphine substituted triangular clusters have attracted

considerable attention mainly because of their catalytic value and their electroactivity and

thermolytic products. Hor and coworkers isolated a tripalladium compound with an Pd3S2 core

shaped in an intriguing ‘Mexican-hat like’ arrangement [42]. The Pd3S2 core can be obtained

through metallation of a Pd2S2 nucleus, similar to the one obtained for [Pd2Ag2(dppf)2( 3-S)2Cl2]

[43]. The dppf ligand exhibits fluxional behavior, despite its large steric bulk and the stability is

imposed on the Pd3S2 core by the triply bridging sulfides. This allows the cooperative

rearrangement of the two dppfs on the Pd3 triangle.

Pd Pd

Ag

Ag

S

S

FeFe

Ph2P

PPh2

Ph2P

PPh2

Cl

Cl

Figure 1.16: [Pd2Ag2(dppf)2( 3-S)2Cl2] showing dppf in chelating mode

The carbonyl exchange reaction of Fe3(μ-S2)CO9 with 1,1’-bis

diphenylphosphino)ferrocene (dppf) in refluxing solvent gives a cluster ligand with a pedant

phosphine moiety, [Fe3(μ-S2)CO9(η1-dppf)]. It has also been observed that under different

reaction conditions, a variety of different substitutions products are obtained, although bridged

cluster forms only in trace quantity (Figure 1.17) [44]

PPh2

PPh2

(CO)2

Fe

Fe(CO)2

S

S

Fe(CO)3Fe

Figure 1.17. [Fe3S2(CO)8(PPh2)2(C5H4)Fe(C5H4)]

Fe

Ph2P (OC)2Fe

(OC)2Fe

S

S

Fe(CO)3

PHPh2

ClAu

Figure 1.18. [Fe3S2(CO)8(PPh2)(C5H4)Au(PPh2)]

One of the recent synthesis has shown that 1,1’-bis(diphenyl phosphine)ferrocene

diselenide (dppfSe2) with [Fe3(CO)12] and [Ru3(CO)12] under the same reaction condition

afforded [Fe3(μ-Se)2(μ2-dppf)(CO)7] and [Ru3(2-Se)2(dppf)(CO)7] respectively [45]. Figure

1.19 shows a bridging ligation whereas Figure 1.20 depicts a chelation coordination to metal

cluster.

Fe

Ph2P PPh2

Ru Ru

M

Se

Se

Figure 1.19. Bridging mode of [Fe3(μ2-Se)2(μ-dppf)(CO)7]

Fe

Ph2P

Ph2P

M M

M

Se

Se

Figure1.20. Chelating mode of[Ru3(2-Se)2(dppf)(CO)7]

Another interesting example of unusual chelating coordination by ferrocenyl-diphosphine

ligand attached to a particular metal ion has been reported by Chatterjee et al. in which it is

observed that room temperature reaction of [(CO)6Fe2( 3-Y)2Pd(PPh3)2] (Y= Se, Te) with

bis(diphenylphosphino)ferrocene (dppf) resulting in ferrocenyl diphosphine containing iron

palladium clusters [(CO)6Fe2(μ3-Y)2Pd{PPh2(5 -C5H4)Fe(

5-C5H4)PPh2})] (Y=Se, Y=Te).

Structural characterization reveals an unusual chelating coordination by ferrocenyl diphosphine

attached to palladium atom (Figure 1.21) [25].

Fe Pd

Ph2P

PPh2

Y

Y

Fe

Fe

OC CO

CO

CO

COOC

Y=Se,Te

Figure 1.21. [(CO)6Fe2(μ3-Y)2Pd{PPh2(5 -C5H4)Fe(

5-C5H4)PPh2})] (Y=Se,Y=Te)

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CHAPTER 2

TRANSITION METAL CLUSTERS

CONTAINING FERROCENYL

DIPHOSPHINE

2.1. Introduction

Transition metal cluster containing non-metal atoms as bridging element are gaining a lot

of research interest, as they show unique structures and novel chemical reactivity, and also they

find application in the field of material science and catalysis [1-4]. When the chalcogens are

incorporated in transition metal carbonyl cluster frameworks a wide variety of bonding modes

are observed which help them to obtain novel structural and reactivity features [5,6]. The iron

chalcogenide clusters, [Fe3(CO)9( -E2)] and [Fe2(CO)6( -E)2] (E= S, Se, Te) are used as the

starting materials for several cluster growth reactions [7-10]. Carbonyl ligands are one of most

common ligands in metal cluster chemistry leading to stabilization of low oxidation state metal

cluster compounds. Other ligands like phosphines attached to the transition metals are found to

be very important in maintaining the electronic and steric properties over a very wide range by

varying the organic group (R) [11]. So the researchers in the field of metal clusters focus more

on the synthesis of transition metal clusters containing phosphine ligands, obtained mostly by

ligand substitution reaction of the carbonyl analogue [12-16]. The diphosphines help in

maintaining the multimetallic framework as well as help in attaching two or more cluster

fragments resulting in cluster stability and structural diversity of higher nuclear cluster. Some of

these phosphine ligands play a major role for the synthesis of polynuclear metal clusters by

linking two or more cluster fragments [17-18]. 1,1′-bis(diphenylphosphino)ferrocene (dppf) was

first synthesized in 1965 by the lithiation of ferrocene with n-butyllithium followed by

condensation with chlorodiphenylphosphine in the presence of N, N, N', N'-

tetramethylethylenediamine (TMEDA). The intimate relationship of clusters with polymetallic

aggregates and oligomers has been extensively studied which enables dppf to find a place in

stabilizing the clusters as well as in attaching two or more cluster fragments. The flexible

diphosphine is an important member of the ferrocenylphosphine family. Dppf forms chelates to

a single metal atom, but it can also act as a monodentate ligand or as a bridge across a metal-

metal bond. F.F. de Biani et al. reported two isomeric nido-clusters [Ru3(μ3-Se)2(dppf)(CO)7]

and [Ru3(μ3-Se)2(CO)7(μ-dppf)] containing a dppf ligand in chelating and bridging mode and

also these kinetically controlled chelated compounds can be converted to the more stable

bridged cluster at high temperature (Figure 2.1) [19].

Ph2P

Fe

Ru

Ru RuSe

Se

Ph2P

(CO)3

(CO)(CO)3 Ph2P PPh2

Fe

Ru

RuRuSe

Se

(CO)3

(CO)2(CO)2

Figure 2.1 [Ru3(μ3-Se)2(dppf)(CO)7] in chelating and bridging mode

Cauzzi et al. reported [Fe3( 3-Se)2(CO)7dppf], it is described to have the bicapped open

triangular structure with Fe3Se2 core and regarded as nido cluster with seven skeletal electron

pairs (Figure 2.2) [20].

(CO)2

(CO)3Fe

FeFeSe

Se

(CO)2

Ph2PPPh2

Fe

Figure 2.2:[Fe3(μ3-Se)2(dppf)(CO)7] in bridging mode

Housecroft and Rheingold et al. described {Ru4B}-dppf cluster in which dppf adopts distinct

pendant coordination modes in [Ru4(CO)11(1-dppf)( 4-BH2) - H )] (Figure 2.3) [21].

(OC)3Ru

(OC)3Ru Ru(CO)3

Ru(CO)2

BH H

H

P

Ph2

Fe

Ph2P

Figure 2.3: [Ru4(CO)11(1-dppf)( 4-BH2) - H )]

Hor et al. discussed the cluster [Fe3(CO)8 (1-dppf)( 3-S)2] containing a sulfido-bicapped

{Fe3} triangular core, with dppf adopting pendant coordination mode. The cluster was

synthesized from the respective [Fe3(CO)9( 3-S)] by means of carbonyl exchange reactions in

the presence of dppf (Figure 2.4) [22].

Fe(CO)2

(CO)3

Fe

S

S

(OC)3Fe

PPh2PPh2

Fe

Figure 2.4: [Fe3(CO)8 (1-dppf)( 3-S)2]

.

Onaka et al. reported the structure of the [Co3(CO)8(1-dppf)(

3-CCH3)] clusters which

possess the trinuclear 3-ethylidyne-capped {Co3} core, having a dppf in pendant mode [23]. It

also functions as “filler” among different cluster fragments and helps in the design of

multimetallic cluster (Figure 2.5).

(OC)3Co

Co

(CO)3

HC

Co(CO)2

PPh2

Fe

PPh2

Figure 2.5. [Co3(CO)8(1-dppf)(

3-CCH3)]

In [Pd3( -dppf)(dppf)(3-S)2Cl2] the structure shows dppf coordinating the Pd metals in both

chelated and bridging mode (Figure 2.6) [24].

Fe

Pd

PdPd

S S

Cl

Cl

P

P

Ph Ph

Ph

Ph

Fe

P

P

PhPh

Ph

Ph

Figure 2.6. [Pd3( -dppf)(dppf)(3-S)2Cl2]·

In view of these interesting bonding features of ferrocenyl diphosphine in cluster

chemistry, we focused our study on the synthesis of homo and heterometallic transition metal

cluster containing chalcogen atoms and ferrocenyl diphosphine ligands in different bonding

modes. We have also been able to use ferrocenyl diphosphine containing cluster for cluster

growth reaction and obtained heterometallic cluster system.

2.2. Experimental Section

2.2.1. General Procedures

All reactions and manipulations were carried out under an inert atmosphere of dry, pre-

purified argon or nitrogen using standard schlenk line techniques. Solvents were purified, dried

and distilled under an argon atmosphere prior to use. Infrared spectra were recorded on a Perkin

Elmer Spectrum RX-I spectrometer as dichloromethane solutions in 0.1 mm path lengths

NaClcell and NMR spectra on a 400 MHz Bruker spectrometer in CDCl3. TLC plates (20x20

cm, Silica gel 60 F254) and W(CO)6 were purchased from Merck. [Fe3Se2(CO)9] and

[Fe3Te2(CO)9], were prepared following reported procedures

2.3. Results and Discussion

The reaction of [Fe3Te2(CO)9] with dppf at room temperature and under argon

atmosphere results in the formation of trinuclear iron - chalcogenide ferrocenyl diphosphine

clusters, [Fe3Te2(CO)9{(PPh2)(C5H4)Fe(C5H4)(PPh2)}] (Te2Red3), while reaction at low

temperature gave another red cluster [Fe3Te2(CO)9{(PPh2)(C5H4)Fe(C5H4)(PPh2)}] (Te2Red1)

containing a ferrocenyl diphoshine unit with monodentate coordination. The cluster (Te2Red1)

has been observed to convert to the stable cluster (Te2Red3) on room temperature stirring. This

shows that (Te2Red1) is an intermediate to the cluster (Te2Red3).

Similar reaction of [Fe3Se2(CO)9] with dppf at room temperature gave only one black

coloured cluster compound, [Fe3Se2(CO)8{(PPh2)(C5H4)Fe(C5H4)(PPh2)}] (Se2Black1).

Further reaction of [Fe3Se2(CO)8{(PPh2)(C5H4)Fe(C5H4)(PPh2)}] (Se2Black1) with

W(CO)5THF results in the formation [Fe3Se2(CO)8(2-dppf) W(CO)5] .

2.4. Conclusion

Coordination behavior of ferrocenyl diphosphine ligands for different types of transition

metal chalcogenide clusters and metal carbonyls have been studied resulting in the control

synthesis of clusters containing unique diphosphine attachment to one metal of a cluster unit as

well as with different metals. Three types of diphosphine coordinated metal clusters have been

obtained, one having hanging uncoordinated phosphorus and other coordinated to the metal,

chelated mode of bonding and the other is interbridging mode of bonding. Synthesis and

characterization of ferrocene containing chalcogenide transition metal clusters (Te2Red1) and

(Te2Red3), (Se2Black1) and (Se2BlackW(CO)5) has been achieved in which (Te2Red1)and

(Se2Black1) shows a diphosphine ligand attached to the metal cluster where one phosphorus is

coordinated with the iron atoms of the cluster and the other phosphorus is hanging

uncoordinated. Compound (Te2Red3) shows the diphosphine ligands in chelating type of

bonding around the iron metal centre. Heterometallic cluster (Se2BlackW(CO)5) shows a

diphosphine ligand attached to the metal cluster where one phosphorus is coordinated with the

iron atoms of the cluster and the other phosphorus is coordinated to the tungsten atom.

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